For numerous applications of radar, it is necessary to know the radar antenna pointing angles with some precision. However, errors in the measurement of antenna pointing direction can be caused by angular errors in the mounting of the antenna to a base. In the case of airborne radar, there are additional antenna pointing errors caused by aircraft attitude measurement errors introduced by the inertial navigation system (INS). While the base mounting errors are fixed, inertial errors are time varying, but on a relatively long time scale. If these errors exceed an allowed tolerance level, it is necessary to estimate the antenna pointing errors so the effects of these errors can be removed from further radar processing or so the antenna can be pointed in a direction that compensates for the error.
A method for estimating antenna tilt errors is described in U.S. Pat. No. 5,485,156 to Manseur, et al., which is incorporated herein by reference. The Manseur patent describes a system limited to using pairs of consecutive antenna scans and comparing returned signals averaged over particular defined regions to derive estimates of pitch, roll and elevation errors. These defined regions are defined by angular sectors about the aircraft location. Each comparison of signals from consecutive scans results in a tilt error measurement that is then filtered. This is limited in its ability to accurately estimate error and accurately correct for it.
Therefore, there exists a need for a method of improving estimation of airborne radar antenna pointing errors and accurately correcting for the errors.